Is cold air mirage real? My son-in-law and his shooting buddies have convinced me it is...
He is part of a group of friends who live in Namibia and hunt springbuck a few times a year, where the distances are sometimes beyond 1000 meters. Chalk pans are dry shallow lakes that fill up once or twice a year after the heavy rains, but most of the year, it is just empty, so you have good visibility and long shots are possible. The springbuck like the better quality grass that grows in and around the chalky deposits (apparently it is more nutritious, and it tastes better!), so early in the morning that’s where they are heading to eat the new growth. We show up before 5 am, get set up prone, and wait for the sun to come up. Eventually a group of 5 to 15 would wander across the pan, we range the distance, run the ballistics, and everybody in the group picks a different one, then count down from 3 to 1, and fire. The 338 and 375 rifles do the best beyond 1200 meters (1,150 yards), but the 6, 6.5 and 7 mm do very well if you are lucky enough to encounter springbuck at the shorter distances.
Getting good accuracy is a challenge in winter that time of the day, as there is an inversion layer (that trapped dust and smoke below it all night) and that eventually flips over, then it suddenly gets cold for 15 minutes, and then goes back to normal again.
We have run the experiment the day before the hunt where you shoot two shots at paper at a time, at 1000 m, and the bullet holes are often side by side, so the load and the gun is good, then wait 10 minutes and do it again. The point of impact walks out 9-12” at an angle related to wind direction, with the two holes still close to each other, then the shots walk back to the starting point. After an hour or so, you are back exactly at the original starting point. Wind speed is usually low (1-5 mph range).
Is this an instance of cold air mirage shifting the sight picture? Or air an downdraught pushing the bullet down?
I never realized stacked cold air layers could also cause mirage. I guess the physics says it must do that if there is a reversed density gradient.
Have you guys experienced this when shooting during the 30 minutes of dusk when the sun comes up? Are we seeing ghosts?
[There is one theory that cold air mirage caused the Titanic crew not to see the ice berg. The ice berg image apparently/allegedly disappeared below the horizon, making it invisible from afar. Opposite effect of a car in the distance appearing to hovering higher than the horizon when you drive on hot tarmac in Arizona on a baking summers day... But who knows what really happened!]
He is part of a group of friends who live in Namibia and hunt springbuck a few times a year, where the distances are sometimes beyond 1000 meters. Chalk pans are dry shallow lakes that fill up once or twice a year after the heavy rains, but most of the year, it is just empty, so you have good visibility and long shots are possible. The springbuck like the better quality grass that grows in and around the chalky deposits (apparently it is more nutritious, and it tastes better!), so early in the morning that’s where they are heading to eat the new growth. We show up before 5 am, get set up prone, and wait for the sun to come up. Eventually a group of 5 to 15 would wander across the pan, we range the distance, run the ballistics, and everybody in the group picks a different one, then count down from 3 to 1, and fire. The 338 and 375 rifles do the best beyond 1200 meters (1,150 yards), but the 6, 6.5 and 7 mm do very well if you are lucky enough to encounter springbuck at the shorter distances.
Getting good accuracy is a challenge in winter that time of the day, as there is an inversion layer (that trapped dust and smoke below it all night) and that eventually flips over, then it suddenly gets cold for 15 minutes, and then goes back to normal again.
We have run the experiment the day before the hunt where you shoot two shots at paper at a time, at 1000 m, and the bullet holes are often side by side, so the load and the gun is good, then wait 10 minutes and do it again. The point of impact walks out 9-12” at an angle related to wind direction, with the two holes still close to each other, then the shots walk back to the starting point. After an hour or so, you are back exactly at the original starting point. Wind speed is usually low (1-5 mph range).
Is this an instance of cold air mirage shifting the sight picture? Or air an downdraught pushing the bullet down?
I never realized stacked cold air layers could also cause mirage. I guess the physics says it must do that if there is a reversed density gradient.
Have you guys experienced this when shooting during the 30 minutes of dusk when the sun comes up? Are we seeing ghosts?
[There is one theory that cold air mirage caused the Titanic crew not to see the ice berg. The ice berg image apparently/allegedly disappeared below the horizon, making it invisible from afar. Opposite effect of a car in the distance appearing to hovering higher than the horizon when you drive on hot tarmac in Arizona on a baking summers day... But who knows what really happened!]
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